I did have all 4 corners of the weld tacked before doing the rest. I wouldn’t think it would matter if I did the corners vs the sides but 
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Yea, my thought for the tilt was to set up fixtures in the right spots and heat it all the way around where it was welded to a cherry red. Then crank on a couple strategically place clamps to make it flatten out. I guess I was looking extra validation that it’s a good plan because I’ve never done it, and it is just based on what I’ve read / seen online.
I gave it a shot last night but was having some trouble with my rosebud tip on the oxy-acetylene torch. After some internet searches and playing around with it, I got a decent blue flame off it. However the steel never got past a deep blue and after a while, the flame started doing funky things. The tanks I borrowed may not be big enough for the rosebud tip. I think I may try just heating it with a cutting tip.
Can I have my clamps put pressure on it before it is heated so then when it heats, it just bends “automatically”? Or is that bad to do and I need to hurry up and clamp it after it is cherry red?
I would think you could do it either way. IF you are having trouble getting it hot enough I would try clamping it first.
I did the clamping first, then got it as hot as I could (though I could only get it to orange), then turned off the torch and cranked the clamps down as hard as I could. While it was hot, it made it flat with no gap. However as it cooled, the gap reappeared, regardless of how hard I clamped. The gap did shrink some. Before a 1/16" shim would fit underneath it and after only a 1/32" shim would fit.
Next I tried just strategically heating different places. Initially that went the other way and took it back to where a 1/16" shim fit in the gap. 
However I tried heating another area and was able to bring it back to just the 1/32" shim fitting. I keep doing that same area but it seems doing it repeatedly didn’t close the gap any further.
I think I may test heating the outside corner where the gap is on a scrap piece to see which way it moves.
Here is a video that may help you understand how heat effects Metal when welding
Here is one that show how to straighten with heat
you can see there is a plate welded to the bottom side of that tube. when welded it would have humped up on the side he is heating. That is because it shrunk on the other side. By heating it on the top side he causes it to shrink and pull back and in turn straighten the tube. This is not something you can just pick up a torch and learn overnight. To do this and be good at it takes lots and lots of trial and error.
This will help you understand why you you got to 1/32" and than went back when you heated the other side.
Here is another one, Keith is a Master at this
Very cool. My youtube search did not bring these up. The laser pointer to test is a great idea. Thanks!